This invention relates to chemically modified elastomers, blends thereof and processes to produce them.
Ethylene-Propylene copolymers and Ethylene-Propylene Diene Monomer (EP(D)M""s) elastomers have been modified by various agents in the past to improve their properties and compatibilities with other polymers. In particular, EP(D)M""s were typically grafted with unsaturated carbonyl derivatives to improve their compatibility to thermoplastics such as polyamides (as taught in U.S. Pat. No. 3,972,961). Thermoplastic components, particularly polyamide components, have been recently introduced in the automotive industry to replace metallic parts. These components, made of high molecular weight thermoplastics are generally glass filled and produced by blow molding. In general, thermoplastics are limited by processing problems. For example, polyamide shows limitations in the blowing phase because of its rather low melt strength which results in parison tear and failure in the blow molding process. High molecular weight modifiers can be used to increase the melt strength, provided however that (1) they can be easily dispersed within the thermoplastic, and (2) they do not increase the blend viscosity and limit the cycle time in the blow molding phase. Thus, there is a need in the art for a thermoplastic modifier that can be easily dispersed and that does not substantially increase the blend viscosity versus traditional modifiers. The invention herein addresses this need by selecting a particular EPDM composition to be grafted and then blended with the thermoplastic. This combination meets the desired EPDM/thermoplastic blend properties without the expected increase in melt viscosity. Moreover, the selected EPDM composition shows increased grafting efficiency versus traditional EPDM compositions having comparable structures.
Art Disclosed for United States Purposes Includes:
JP 04220409 which discloses grafting styrene/acrylonitrile mixture onto a blend of EPDM""s of differing glass transition temperatures and U.S. Pat. No. 5,374,364 which discloses grafting EPDM with various monomers including crotonaldehyde.
This invention relates to a composition comprising an ethylene-higher xcex1-olefin polymer composition grafted with at least 0.05 weight %, preferably at least 1 weight %, based upon the weight of the polymer, of an unsaturated organic compound containing at least one carbonyl group, wherein-the ethylene-higher xcex1-olefin composition comprises:
i) a first polymer fraction having a number average molecular weight of from 10,000 to 500,000, an ethylene content of from 30 to 80 weight % and a diene content of from 1.0 to 12 weight %, based upon the weight of the polymer; and
ii) a second polymer fraction having a number average molecular weight of from 100,000 to 10,000,000, an ethylene content of from 40 to 90 weight % and a diene content of from 0 to 12 weight %, based upon the weight of the polymer; provided that:
a) the second fraction has a higher molecular weight than the first fraction,
b) the second fraction has an equal or higher ethylene content than the first fraction,
c) the weight ratio of diene in the first fraction to diene in the second fraction is at least 0.5/1, preferably 1/1, more preferably 2/1,
d) the Mw/Mn of each fraction is independently from 2 to 6.5, and
e) the first fraction comprises 60 to 95 weight % of the total polymer composition.
This invention further relates to blends comprising the composition described above and one or more polymers selected from the group consisting of polyamides, polypropylenes, polyethylenes, ethylene-propylene copolymers, and ethylene-propylene-diene copolymers.